I will use a used drive for a desktop. All of them are backed up by the server and generally you can tell when a mechanical drive is failing (clicking noises). I have not tried a used SSD because the cost differential did not make it worthwhile (although some of my older machines are sporting 64G SSDs). Of course I don't have my desktops in raid.
The only problem with using them on the server is that I kind of leave it alone and ignore it once it's set up. Raid would mitigate failure, but I might not notice until too late.
How reliable are used SSDs and how can you tell they are failing?
